It’s widely believed that snowy owls that winter south of the Arctic tend to be struggling, starving birds that only move south because they can't find enough to eat at home. That is not necessarily the case, a recent study suggests.

Researchers from the University of Saskatchewan in Canada tracked snowy owls wintering in Canada and found that while age and sex affect the birds' condition, most do fairly well, showing few signs of starvation and some even putting on weight over the winter months.

The study was published in the October issue of the American Ornithological Society’s journal, The Auk: Ornithological Advances.

Female snowy owls are bigger than males, and the researchers expected that their dominant behavior would give females access to greater food resources during the challenging winter season. Their results bore this out—females tended to be in better condition than males, and adults, with their greater hunting experience, tended to be in better condition than juveniles.

Surprisingly, many of the adult birds in the study actually increased their fat stores slightly over the course of the winter. Well-insulated against the cold and not distracted by the demands of reproduction, snowy owls may use winter as a time to recharge and build up their reserves before returning to their breeding grounds.